1. Field of the Invention
The present invention relates to a cutting machine for cutting a flat workpiece, which comprises a cutting table having a working surface for supporting the flat workpiece, a support movable substantially parallel to the working surface, and a cutting unit mounted on the support above the working surface, the cutting unit comprising a cutting knife vertically adjustable relative to the working surface to regulate the cutting depth of the knife, a vertically displaceable carriage for the cutting knife for vertically adjusting the knife, a cutting knife holder rotatable about a vertical axis for orienting the knife in a desired direction, and drive means actuatable for displacing the carriage, rotating the holder and moving the support in response to a programmable control.
2. Description of the Prior Art
Cutting machines of this type permit the cutting depth of the knife to be exactly controlled so that, for example, a multi-ply flat workpiece may be so cut that only a predetermined number of plies are penetrated by the knife while plies underlying the cut plies remain integral. This may be of particular importance in cutting patterns out of laminates since this requires the carrier layer to remain uncut. Such cutting machines operate very well with cutting knives vibrated by ultrasound frequencies. To set the cutting depth of the knife accurately it is required to determine the exact vertical distance of the cutting knife edge from the working surface whereon the flat workpiece is placed and to be able to determine a reference point for the desired vertical adjustment. This has been done heretofore by carefully lowering the vertically displaceable cutting knife carriage towards the working surface until the cutting knife edge touches a measuring strip on the working surface. This is a very time-consuming operation and, furthermore, does not assure the desired accuracy of the setting. Since the cutting knife must be re-set after each change of knives and even during the use of one knife to correct the wear of the knife edge, this adjustment operation considerably slows the entire cutting operation.
In addition, since the knife must be tangentially guided along a cutting line to obtain the desired pattern, the angular position of the knife must also be set and the control must receive a signal determining a reference point for the angular setting of the cutting knife.